Abstract: A three-dimensional numerical model is developed to simulate and analyze the internal erosion process of soils. It adopts a discrete element method (DEM) to calculate particle dynamics and a finite volume method (FVM) to calculate seepage flow, and couples these two fields together through related closure terms. Its simulation results presented herein reproduce the rheological behaviors in the classic experiments, and we can set up a relationship of soil stability versus its effective frictional coefficient μeff. And we have found the soils become unstable immediately after water head exceeding its threshold Hc. Under a loaded water head less than Hc, μeff is nearly equal to μ0 and the soils remain stable, with no internal erosion motivated; while as it is increased up to Hc, μeff abruptly jumps to μ1 or an even higher level, and accordingly an internal erosion process is triggered off (μ0 and μ1 are numerically calibrated values). The findings in this paper would highlight the mechanism of internal seeping erosion in levees and earth dams.

Key words: internal erosion, numerical model, rheological behavior, abrupt instability, threshold